The present invention relates to assist straps for automobiles and the like. Such assist straps are in wide use and are both decorative and functional. As to function, the assist straps are located strategically within the vehicle, e.g., on the back of the front seats of the vehicle, above the doors of the vehicle, on the inside panel of the doors of the vehicle, and/or adjacent the doors of the vehicle. In use, the occupants of the vehicle tend to exert forces on the straps in nearly every conceivable direction, at times pulling outwardly on the straps, at times pushing downwardly on the top of the straps, at times pushing upwardly on the straps and at times applying such forces in combination or in sequence. These forces are reoccuring over the life of the vehicle. By virtue of these reoccurring forces, a small, but significant, percentage of these assist straps become loose at their attachment points. Any such looseness not only detracts from the decorative appearance of the straps, but more importantly, detracts from the secure feel of the straps. Moreover, in view of the very prominent nature of the straps in the interior of the vehicle, and the frequency with which these straps are either observed or used, looseness of the mounts for these straps has a deleterious effect on the vehicle owner's appreciation of his vehicle and his perception of the quality of the vehicle. Thus, the reputation of the manufacturer of the vehicle is affected by this problem, at least to some degree. In all the years in which this problem has been experienced by the automobile manufacturers and users, no acceptable solution has been devised.
Although many lock-type fasteners are presently known which would alleviate the problem of loose assist straps, none are believed to constitute a commercially-acceptable solution to the above problem. It must be borne in mind that these assist straps are attached in massive quantities. Some popular vehicles use as many as nine assist straps. Consequently, the high volume of production must be accommodated in any commercially-acceptable solution to this problem.
Generally speaking, a solution to this problem should not require the addition of a part to the strap-fastening structure. For example, the use of a lock-washer, star-washer or the like would not only involve additional costs for the additional part, but would complicate the movement of parts to the assembly line and the manipulations of the assembler at the assembly line. Furthermore, whenever an additional part is required, there always exists the possibility that the part will be inadvertently omitted in the assembly process.
Complicating this problem is the fact that the threaded fasteners used to secure assist straps often bear upon relatively soft materials such as injected-molded plastics or die-cast soft metals. Many of the currently-available lock systems for fasteners are either not effective on such soft materials or tend to erode those materials. It will be appreciated that a lock-system must be effective on such soft materials and must not deleteriously deform or erode the soft material.
Considering the current substantial life of an automobile, the many cycles of application of considerable forces to assist straps, the variety of directions through which these forces are applied, the variety of sequences of application of these directional forces, and the problems of cost and mass production, it is readily understood why this problem has existed for so long without a commercially-acceptable solution. It is believed that the present invention provides a commercially-acceptable solution to the problem of loosening of the assist strap mounting structures. In particular, it does not require any additional fastening parts, can be implemented using existing assembly techniques and equipment, requires little change in the tooling used to manufacture the sub-components of the assist strap fastening structure, can be used with relatively-soft materials such as injection molded plastics and die cast metals, and is relatively inexpensive to implement. Moreover, the present fastener lock system allows removal of the strap should the strap need replacement.
In essence, the present invention utilizes the same type of threaded fasteners previously used to secure the assist straps. However, one surface of the fastener is provided with relatively-deep grooves or recesses and the mating surface of the assist strap component is provided with correlative ridges or peaks which mate with the grooves or recesses on the threaded fastener. The depth of the recesses, and the angles thereof, are selected to provide a "camming" action which increases the force required to back off the threaded fastener, yet does not damage the threaded fastener or the mating strap component. The ridges and recesses may be slightly rounded when the mating component is made of a soft material such as injected-molded plastic or die-cast metal to avoid substantial gouging or erosion of the mating component. It is believed that this solution to a long standing problem is not only efficient and effective, but is also elegant in its simplicity.
Other features and advantages of the present invention will be made apparent in view of the following detailed description of the preferred embodiments.